Middle Jurassic Palynoflora and its Palaeoenvironmental Implication in Turpan Depression, Xinjiang

Wang Yongdong; Jiang Dexin; Yang Huiqiu; Sun Feng

The terrestrial sediments are well developed in the Turpan-Hami Basin in eastern Xinjiang, whichshow the important petroliferous and coal-bearing significance. Abundant fossil spores and pollen grainsof 97 species assigned to 45 genera are recovered from the Middle Jurassic Xishanyao, Sanjianfang andQiketai Formations of Boreholes PU1 and CN1 in Turpan depression. Three palynological assemblagezones representing Aalenian to Bajocian, early Bathonian and late Bathonian are recognized as: 1) Cy-athidites- Cycadopites- Quadraeculina( CCQ) Zone; 2)Cyathidites- Classopollis-Piceites ( CCP) Zone and 3)Granulatisporites- Classopollis-Podocarpidites( GCP) Zone. The Middle Jurassic palynoflora is dominantedby conifers, ginkgo- cycads as well as ferns. From Aalenian-Bajocian to late Bathonian, ferns representedby Cyatheaceae, Dicksoniaceae and Osmundaceae gradually decreased, while conifers includingConiferales, Pinaceae, Podocarpaceae and especially Cheirolepidiaceae increased in abundance. The paly-noflora indicates a warm and humid climate in Aalenian to Bajocian, and somewhata semi-arid and hotclimate condition in early to middle Bathonian. The warm- humid climate is favorable for the accumula-tion of coal, oil and gas resources,while the arid and hot climate results in the weakness and even termi-nation of hydrocarbon formation.

1 Nanjing Institute of Geology and Palaeontology,Academia Sinica,Nanjing 210008;

2 Lanzhou Institute of Geology,Academia Sinica,Lanzhou 730000

Received Date: 1997-05-13

Key words:

Abstract: The terrestrial sediments are well developed in the Turpan-Hami Basin in eastern Xinjiang, whichshow the important petroliferous and coal-bearing significance. Abundant fossil spores and pollen grainsof 97 species assigned to 45 genera are recovered from the Middle Jurassic Xishanyao, Sanjianfang andQiketai Formations of Boreholes PU1 and CN1 in Turpan depression. Three palynological assemblagezones representing Aalenian to Bajocian, early Bathonian and late Bathonian are recognized as: 1) Cy-athidites- Cycadopites- Quadraeculina( CCQ) Zone; 2)Cyathidites- Classopollis-Piceites ( CCP) Zone and 3)Granulatisporites- Classopollis-Podocarpidites( GCP) Zone. The Middle Jurassic palynoflora is dominantedby conifers, ginkgo- cycads as well as ferns. From Aalenian-Bajocian to late Bathonian, ferns representedby Cyatheaceae, Dicksoniaceae and Osmundaceae gradually decreased, while conifers includingConiferales, Pinaceae, Podocarpaceae and especially Cheirolepidiaceae increased in abundance. The paly-noflora indicates a warm and humid climate in Aalenian to Bajocian, and somewhata semi-arid and hotclimate condition in early to middle Bathonian. The warm- humid climate is favorable for the accumula-tion of coal, oil and gas resources,while the arid and hot climate results in the weakness and even termi-nation of hydrocarbon formation.

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Reference (20)

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Middle Jurassic Palynoflora and its Palaeoenvironmental Implication in Turpan Depression, Xinjiang

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